Generally, Multiple-Input Multiple-Output (MIMO) technology will hereinafter be described in detail. In brief, MIMO is an abbreviation for Multi-Input Multi-Output. MIMO technology uses multiple transmission (Tx) antennas and multiple reception (Rx) antennas to improve the efficiency of transmission/reception (Tx/Rx), whereas the conventional art generally uses a single transmission (Tx) antenna and a single reception (Rx) antenna. In other words, MIMO technology allows a transmitting end and a receiving end to use multiple antennas so as to increase capacity or improve performance. If necessary, MIMO technology may also be called multi-antenna technology. In order to correctly perform multi-antenna transmission, the MIMO system has to receive feedback information regarding channels from a receiving end designed to receive multi-antenna channels.
Various feedback information fed back from the receiving end to the transmitting end in the legacy MIMO wireless communication system may be defined, for example, a rank indicator (RI), a precoding matrix index (PMI), channel quality information (CQI), etc. Such feedback information may be configured as information appropriate for legacy MIMO transmission.
There is a need for a new system including the extended antenna configuration as compared to the legacy MIMO wireless communication system to be developed and introduced to the market. For example, although the legacy system can support a maximum of 4 transmission antennas, new systems have an extended antenna configuration that supports MIMO transmission based on 8 transmission antennas, resulting in increased system capacity.